Social concern about environmental problems such as inhibition of carbon dioxide exhaust is demanded. In response to this demand, there is an increasing demand for development of materials having low rolling resistance and materials having sufficient abrasion resistance and fracture characteristics due to superior wet skid resistance as materials for vehicle tires, in particular, tire treads contacting the road.
Meanwhile, carbon black, silica and the like are used as reinforcements for tire treads. When silica is used as a reinforcement, advantageously, hysteresis loss is reduced or wet skid resistance is improved. As compared to carbon black having a hydrophobic surface, silica having a hydrophilic surface has a disadvantage of low dispersibility in rubber due to low affinity to conjugated diene rubbers. Accordingly, use of an additional silane coupling agent is required to improve dispersiability of silica in rubbers or to form silica-rubber bonds.
In order to solve these problems of silica, functional groups having affinity to or reactivity with silica are introduced into an end of rubber molecules having high mobility to improve dispersiability of silica in conjugated diene rubbers and seal the end of rubber molecules by bonding to silica particles and thereby reduce hysteresis loss.